Nuova ricerca

VALENTINA NICOLINI

Personale tecnico amministrativo
Dipartimento di Scienze Chimiche e Geologiche - Sede Dipartimento di Scienze Chimiche e Geologiche

Home |


Pubblicazioni

2019 - Mesoporous bioactive glasses doped with cerium: Investigation over enzymatic-like mimetic activities and bioactivity [Articolo su rivista]
Nicolini, V.; Malavasi, G.; Lusvardi, G.; Zambon, A.; Benedetti, F.; Cerrato, G.; Valeri, S.; Luches, P.
abstract

In this work, we investigate the ability of mesoporous bioactive glasses (MBGs) modified with cerium ions (Ce3+/Ce4+) to act as catalase and superoxide dismutase (SOD) mimetic materials. We have previously reported that the catalytic properties of bioactive Ce-containing glasses based on 45S5 Bioglass® and synthesized via melting are influenced by: i) composition (presence/absence of P2O5); ii) Ce3+/Ce4+ molar ratio. The introduction of cerium species drastically decreased the bioactivity in terms of Hydroxyapatite formation during bioactivity tests in vitro. We thus decided to add cerium to MBGs, a class of glasses with improved bioactivity with respect to classical molten glasses. MBGs exhibit a high surface area and their reactivity is increased with respect to the molten glasses; they are able to induce the formation of Hydroxyapatite over the surface within shorter times with respect to the 45S5. The catalase and SOD mimetic activity tests revealed that the Ce-MGBs are able to act as mimetic materials for the two enzymes. Both Infrared Spectroscopy and X-ray diffraction analysis have confirmed the presence of Hydroxyapatite over both 80SiO2–15CaO–5P2O5, and 80SiO2–20CaO MBGs samples modified by 5.3% mol of CeO2; simultaneously the glasses maintain a good catalase activity. Moreover, the 80SiO2–15CaO–5P2O5 potential bioactive glasses showed SOD mimetic activity. These results highlight that it is possible to obtain a glass with both antioxidant and bioactivity properties.

2018 - Role of cerium oxide in bioactive glasses during catalytic dissociation of hydrogen peroxide [Articolo su rivista]
Benedetti, Francesco; Amidani, Lucia; Pelli Cresi, Jacopo Stefano; Boscherini, Federico; Valeri, Sergio; D'Addato, Sergio; Nicolini, Valentina; Malavasi, Gianluca; Luches, Paola
abstract

The addition of cerium oxide to bioactive glasses, important materials for bone tissue regeneration, has been shown to induce multifunctionality, combining a significant bioactivity with antioxidant properties. We provide a real time investigation of the evolution of the electronic properties of highly diluted cerium ions in a liquid environment containing hydrogen peroxide - the most abundant reactive oxygen species in living cells. This challenging task is undertaken by means of high-energy resolution fluorescence detected by X-ray absorption near-edge spectroscopy at the Ce L-3 edge. We investigate samples with variable compositions and different morphologies. We relate the observed spectroscopic changes not only to variations in the concentration of the two Ce oxidation states in the samples, but also to changes in the local atomic environment of Ce ions, providing a clear picture of the role of cerium ions in the dissociation of hydrogen peroxide. The obtained results contribute to the understanding of the mechanisms that come into play in the process and provide a basis for the optimization of the functionalities of this class of materials.

2017 - Cerium-doped bioactive 45S5 glasses: spectroscopic, redox, bioactivity and biocatalytic properties [Articolo su rivista]
Nicolini, Valentina; Malavasi, Gianluca; Menabue, Ledi; Lusvardi, Gigliola; Benedetti, Francesco; Valeri, Sergio; Luches, Paola
abstract

The ability of Ce-containing bioactive glasses, based on 45S5 Bioglass®, to inhibit oxidative stress in terms of reduction in hydrogen peroxide and superoxide (O2−), by mimicking the catalase and superoxide dismutase activity is reported in this work. The characterization is performed on the powders of pristine glasses and after the soaking in H2O2solutions and simulated body fluid. The glass samples are analysed by XPS, XRD, UV–Vis and FT-IR. The best catalyst activities are obtained for the glass with the highest content of cerium (H_5.3 = 5.3 mol% of CeO2in the nominal glass composition), and the best Ce3+/Ce4+ratio in terms of catalase mimetic activity is found to be a function of H2O2concentration. Moreover, the detailed study of the surface during the mimic enzymatic activity tests shows the formation of a Ca-P-rich layer on the glass surface, where the presence of Ce ions favours the formation of CePO4. The phosphate in turn inhibits the formation of hydroxyapatite, decreasing the bioactivity of the glass with the highest of CeO2in the glass composition. This work shows the effect of Ce3+/Ce4+ratio towards the catalase mimetic activity and for the first time the superoxide dismutase mimetic activity of Ce-containing 45S5-derived glasses.

2017 - Structure of active cerium sites within bioactive glasses [Articolo su rivista]
Benedetti, Francesco; Luches, Paola; D'Addato, Sergio; Valeri, Sergio; Nicolini, Valentina; Pedone, Alfonso; Menziani, Maria Cristina; Malavasi, Gianluca
abstract

The inclusion of small amounts of cerium within the matrix of bioactive glasses, a class of materials used for bone tissue reparation and regeneration, adds a very important antioxidant property. In this work we investigate the local structure around cerium ions in cerium oxide doped bioactive phosphosilicate and silicate glasses, by X-ray absorption fine structure at the Ce K-edge, combined with classical molecular dynamics (MD) simulations. The local structure of the active Ce sites results significantly different from the one in bulk cerium oxide phases. A contracted Ce–O first shell distance with respect to bulk oxides is detected, in full agreement with the results of MD simulations. The cerium environment in the glass matrix at different stages of the reaction with H2O2 does not show significant modifications, in spite of the very high catalytic activity. The accurate description of the active Ce sites within bioactive glasses reported in this work is an important step toward an atomic scale understanding of the material functionalities.

2016 - CATALYTIC BIOACTIVE GLASSES: CATALASE MIMETIC ACTIVITY, AN EXAMPLE [Articolo su rivista]
Malavasi, Gianluca; Nicolini, Valentina; Gambuzzi, Elisa; Menabue, Ledi; Lusvardi, Gigliola; Pedone, Alfonso; Benedetti, Francesco; Luches, Paola; D'Addato, Sergio; Valeri, Sergio
abstract

The ability of a Ce-containing bioactive glasses to inhibit oxidative stress in terms of reduction of H2O2, by mimicking the catalase enzyme activity is demonstrated for the first time. The antioxidant properties of bioactive glasses containing CeO2 have been evaluated by following the degradation of hydrogen peroxide with time after immersion in H2O2 aqueous solutions with different concentration. XPS, UV-Vis and magnetic measurements allowed us to determine the Ce3+/Ce4+ ratio (bulk and surface) and to correlate it with the ability of the samples to show catalase mimetic activity. We have found that the bioactive glass (23.2Na2O-25.7CaO-43.4SiO2-2.4P2O5-5.3CeO2) immersed in 0.1M H2O2 aqueous solution is able to degrade 90% of it in one week.

2016 - SiO2-CaO-P2O5 bioactive glasses: A promising curcuminoids delivery system [Articolo su rivista]
Nicolini, Valentina; Caselli, Monica; Ferrari, Erika; Menabue, Ledi; Lusvardi, Gigliola; Saladini, Monica; Malavasi, Gianluca
abstract

In this paper, we report the study of the loading and the release of curcuminoids by bioactive glasses (BG) and mesoporous bioactive glasses (MBG). Through a detailed spectroscopic study, it was possible to determine the amount and the type of molecules released in water and in simulated body fluid (SBF). In particular, curcumin and K2T21 show a good ability to be released in di-keto and keto-enolic form, depending from the pH. However, after 24 h, the amount of pristine curcumin release is very low with a consequent increment of degradation products derived by curcuminoids. The presence of -OH groups on curcuminoids is a fundamental pre-requisite in order to obtain a high loading and release in polar solution such as water and SBF. The substrate on which we loaded the drugs does not seem to affect significantly the loading and the release of the drugs. The environment, instead, affects the release: for all the drugs, the release in SBF, buffered at pH of 7.4, is slightly worse than the release in water (basic pH values).

2016 - The effect of composition on structural, thermal, redox and bioactive properties of Ce-containing glasses [Articolo su rivista]
Nicolini, Valentina; Varini, Elena; Malavasi, Gianluca; Menabue, Ledi; Menziani, Maria Cristina; Lusvardi, Gigliola; Pedone, Alfonso; Benedetti, Francesco; Luches, Paola
abstract

The effect of phosphate on the ability of Ce-containing bioactive glasses to inhibit oxidative stress was studied on compositions based on Hench (46.2%SiO224.3%Na2O26.9ÊO2.6P2O5, mol%) and Kokubo (50.0%SiO225.0%Na2O25.0ÊO) glasses. In particular, the reduction of catalase mimetic activity of Ce-containing glasses due to the presence: i) of P2O5 in the glass compositions, and ii) of phosphate groups in the solution employed for catalase mimetic activity tests was explained and rationalized by combining SEM, XPS, XRD, DTA, FT-IR and UV-vis experiments with Molecular Dynamics simulations.The results suggest that the Ce ions play a different structural role in the two series of glasses. In particular, in phosphate free glasses Ce is coordinated by non-bridging oxygens (NBOs) originated from the disruption of the silicate network, whereas in phosphate containing glasses the NBOs around Ce ions belong to orthophosphate groups. The latter groups stabilize the Ce3+ species subtracting them from the interconversion process between Ce3+ and Ce4+, which is of fundamental importance for the exhibition of the catalase mimetic activity.

2015 - Evidence of catalase mimetic activity in ce(3+)/ce(4+) doped bioactive glasses [Articolo su rivista]
Nicolini, Valentina; Gambuzzi, Elisa; Malavasi, Gianluca; Menabue, Ledi; Menziani, Maria Cristina; Lusvardi, Gigliola; Pedone, Alfonso; Benedetti, Francesco; Luches, Paola; D'Addato, Sergio; Valeri, Sergio
abstract

The ability of Ce-containing bioactive glasses to inhibit oxidative stress in terms of reduction of hydrogen peroxide, by mimicking the catalase enzyme activity is demonstrated here for the first time. The antioxidant properties of three bioactive glasses containing an increasing amount of CeO2 have been evaluated by following the degradation of hydrogen peroxide with time after immersion in H2O2 aqueous solutions with different concentration. XPS and UV-vis measurements allowed us to determine the Ce(3+)/Ce(4+) ratio in the bulk and on the glass surface, and to correlate it with the ability of the samples to show catalase mimetic activity. Interestingly, we have found that the bioactive glass with composition 23.2Na2O-25.7CaO-43.4SiO2-2.4P2O5-5.3CeO2 immersed in 0.1 M H2O2 aqueous solution is able to degrade 90% of it in 1 week. The reduction in bioactivity of the glasses with increasing CeO2 content is here rationalized in terms of a lower amount of phosphate groups available for the hydroxyapatite layer formation, after binding with cerium ions. In fact, classical molecular dynamics simulations revealed that the addition of CeO2 leads to the formation of cerium phosphate rich regions. The formation of an insoluble CePO4 crystalline phase is also observed by XRD analysis after thermal treatment of the glass samples.

2014 - Biovetri come potenziali drug delivery systems ed impianti con proprietà antiossidanti [Capitolo/Saggio]
Nicolini, Valentina; Malavasi, Gianluca; Ferrari, Erika; Benedetti, Francesco; Luches, Paola; Lusvardi, Gigliola; Castagnetti, Mattia; Valeri, Sergio; Saladini, Monica; Menabue, Ledi
abstract

Fra i biomateriali (“materiali progettati per essere usati a contatto con tessuti viventi, organismi o microorganismi”, definizione IUPAC), i biovetri ricevono un interesse sempre maggiore. Tali materiali trovano infatti largo impiego in chirurgia odontoiatrica ed ortopedica, nella produzione di impianti dentali, protesi o riempitivi ossei. Attualmente l’interesse è rivolto soprattutto ai biovetri di seconda e terza generazione: biovetri che oltre a formare un legame chimico coi tessuti che li circondano, sono capaci di indurre una specifica risposta a livello molecolare nei tessuti stessi, come l’osteoinduzione. I biovetri possono essere prodotti con processi ad alte temperature (metodo per fusione) o a basse temperature con i metodi Sol-Gel, ottenendo in questo caso biovetri porosi o con il metodo EISA ottenendo biovetri mesoporosi. Attualmente presso il nostro laboratorio due sono le linee di ricerca sui biomateriali: i) sintesi di biovetri Sol-Gel (BGSG) ed EISA (MBGSG) e verifica della possibilità di impiegarli come drug delivery systems (DDS) di molecole con proprietà antitumorali, quali i curcuminoidi; ii) sintesi per fusione di biovetri a partire dal vetro 45S5, drogati con CeO2 al fine di verificare la Catalase e SOD mimic-like activity di tali sistemi. Sui vetri porosi e mesoporosi, caricati con curcumina ed un suo derivato (K2T21) sono stati effettuati test di rilascio statico e dinamico in SBF. I rilasci sono stati quantificati ed in entrambi i casi le concentrazioni raggiunte dai farmaci nell’organismo sono nell’ordine del micromolare, ovvero sufficienti per manifestare l’attività antitumorale. Per ciò che concerne la valutazione della Catalase mimic-like activity, sono stati condotti test con H2O2 ed è stato verificato che i biovetri ottenuti per fusione manifestano questa proprietà. Sono inoltre in atto misure di rilascio di cerio in acqua e soluzione di SBF.